Sandblasting is one of the conventionally known processing methods for forming designs on the surface of glass, marble, plastic, ceramic, leather, wooden, and other bases. In general, such engraving for forming a design is carried out either by sandblasting in which a sandblast resist is formed on the surface of a base and the exposed parts not covered with the resist are selectively abraded by blowing an abrasive material or the like against those parts, or by etching with a reagent. In particular, the sandblasting technique in which a mask pattern is formed from a photosensitive resin layer as a sandblast resist by photolithography and selective abrasion is conducted by blowing an abrasive material or the like or the engraving technique based on etching with a reagent is used as a fine processing technique in the formation of a circuit board where a metal pattern and an insulation pattern are coexist, especially in plasma display fabrication for forming a metal wiring pattern and an insulation pattern made of a ceramic, a phosphor, and the like. The photosensitive resin compositions for use in the precision sandblasting are required not only to give cured resin compositions which have sufficient sandblasting resistance to prevent a mask damage by sandblasting, but also to be easily developed with a weakly alkaline aqueous solution after pattern-wise exposure and to pose no problem concerning the working atmosphere, wastewater treatment, and the like. Moreover, the photocured resin compositions are required to be free from base damages caused by a discharge or thunderbolt resulting from static build-up or static electricity generated by friction with fine abrasive particles during sandblasting, e.g., spotting, chipping, or cracking in glass or marble bases and short-circuiting in circuit boards resulting from wiring pattern or insulation layer damages. Photosensitive resin compositions for sandblast resist which are intended to meet such requirements have been proposed. For example, a photosensitive resin composition comprising an unsaturated polyester, an unsaturated monomer, and a photopolymerization initiator is disclosed in JP-A-55-103554 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), and a photosensitive resin composition comprising poly(vinyl alcohol) and a diazo resin is disclosed in JP-A-2-69754.
However, the photosensitive resin compositions for sandblast resist described above have drawbacks in that they are susceptible to static build-up, although excellent in sandblasting resistance and other properties. Therefore, when those compositions were used to conduct fine processing, the accumulated static electricity caused a discharge or thunderbolt to damage the base. In particular, in the formation of a circuit board, the discharge or thunderbolt causes unrepairable defects in the wiring pattern or insulation layer, and this often results in the occurrence of defectives.